JPH03183461A - Sterilization by microwave heating - Google Patents

Abstract

PURPOSE:To sterilize in a short time with stable effect by holding a heating object on a supporting member made of a microwave-transmission material while heating the supporting member at or above the sterilization temperature prior to the microwave-sterilization. CONSTITUTION:A supporting member made of a microwave-transmission material is heated at or above the sterilization temperature (preferably >=130 deg.C) in advance, a packaged material filled with the heating object is placed on the supporting member and the object is sterilized by microwave heating.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a microwave heating sterilization method for heat-cooked foods, and particularly a method for heating a support for microwave heating to a sterilization temperature or higher. The present invention relates to a microwave heat sterilization method for preventing heat radiation from the surface of a package filled with a heated object and obtaining a stable sterilization effect by using a heated object.

<Prior Art> Many methods of heating and sterilizing foods using microwaves are known, but conventionally, when sterilizing foods using microwaves, little consideration has been given to so-called preheating, in which the support is heated in advance.

<Problems to be Solved by the Invention> However, in the conventional heat sterilization method described above, a stable sterilization effect was not obtained. The reason is that with microwave heating, items with large dielectric loss such as foods are heated by their own heat generation, but items with small dielectric loss such as supports are not heated, so the amount of heat of the heated object is transferred from the surface to the support. This is because the heat is transmitted and escapes, and heating near the surface of the object in contact with the support is delayed, resulting in poor sterilization.

In addition, if the surface of the object to be heated is heated to reach the sterilization temperature in order to sufficiently sterilize the object, microwave irradiation must be performed for a long time, which consumes a significant amount of energy. There was an issue with the problem of overflowing.

In microwave heat sterilization, when an object to be heated is sterilized with microwaves, heat is emitted from the part of the surface of the object that is in contact with a support, thereby causing a delay in heating near the surface of the object. It is an object of the present invention to disclose a microwave heat sterilization method that prevents the occurrence of sterilization defects and makes it possible to save energy consumption by reducing the microwave irradiation time.

<Means for Solving the Problems> The present invention has been developed to solve the above problems, and includes a support body made of a microwave-permeable material and having a storage section in the center, in which an object to be heated is placed. Microwave heat sterilization is a microwave heat sterilization method in which a package filled with is housed and sterilized by irradiation and heating with microwaves, in which the support is preheated to a sterilization temperature or higher. This problem could be solved by disclosing a method. Moreover, this effect is further exhibited by heating the package filled with the object to be heated to a temperature at which sterilization failure can be prevented.

The present invention will be further explained. The material constituting the support may be any material that transmits microwaves and has heat resistance and pressure resistance (bending strength), such as a silicone-impregnated glass cloth laminate, an unsaturated polyester sheet molding compound, etc. Reinforced plastic is suitable.

The holder may be made of any material that has bending strength and tensile strength, preferably a microwave i3-permeable material such as glass-filled epoxy resin.

The package is a bag or tray filled with food that has been warmed and heated, and the material is made of a laminated material that can withstand the internal pressure increase due to high temperature sterilization, is microwave permeable, and has a heat-sealable inner surface. Become.

In the case of bags, the specific laminated materials include stretched nylon/unstretched nylon/unstretched polypropylene, polyethylene terephthalate/polyvinylidene chloride/unstretched polypropylene, stretched nylon/polyvinylidene chloride/unstretched polypropylene, and polyethylene terephthalate/unstretched polypropylene. Films with a composition of ethylene vinyl alcohol copolymer/unstretched polypropylene, stretched nylon/ethylene vinyl alcohol copolymer/unstretched polypropylene, polyvinylidene chloride coated polyethylene terephthalate/nylon/unstretched polypropylene, etc., with a total thickness of about 60 to 150.
It is appropriate that it is μ. In addition, in the case of a tray, the lid material is
A configuration similar to the above can be used.

The container body is made of unstretched polypropylene, unstretched polypropylene/saponified ethylene-vinyl acetate copolymer/unstretched polypropylene, unstretched polypropylene/unstretched nylon/saponified ethylene-vinyl acetate copolymer/unstretched polypropylene, polypropylene/ Materials such as ethylene vinyl alcohol copolymer/polypropylene, polycarbonate/ethylene vinyl alcohol copolymer/polypropylene, crystalline polyethylene terephthalate/ethylene vinyl alcohol copolymer/polypropylene are suitable, and the wall thickness after the bottom shape is 2. It is appropriate that it is less than Orm.

Then, the structures of the support, bag, and tray will be explained according to the drawings.

FIG. 1 shows a perspective view of the support 1. Further, FIG. 3 is a sectional view taken along the line AA of the package 2 housed in the support 1. As can be seen, the support l has a pressing part 3 on the periphery and is made up of a bottom wall 12 and an upper wall 11 forming a storage part 4 having approximately the same shape as the appearance of the package 2 to be stored in the center. Become.

FIG. 2(a) shows a perspective view of the bag 5. The bag 5 has a structure in which the corners are sealed in an arc shape.

A perspective view of the tray 6 is shown in FIG. 2(b). The tray 6 has a structure in which a lid material 14 is superimposed on a container body 13.

Next, heating of the support will be explained. The heating of the support is called preheating, in which the support is heated in advance to a sterilization temperature or higher, which is 4 degrees Celsius. this is,
When an object to be heated is stored in a support at room temperature and sterilized by heating with microwaves, the heat from the heating movement radiates from the vicinity of the surface in contact with the support, causing a delay in heating and resulting in poor sterilization. This is to prevent A suitable temperature for this preheating may be 130° C. or higher.

When heating the object to be heated, the difference between the highest temperature point and the lowest temperature point can be reduced by reducing the temperature increase width during heat sterilization with microwaves, and the surface of the object to be heated can be heated beforehand. It is very effective in that it can remove body heat and reduce the effect of lowering the temperature of the support as much as possible. The heating of the object to be heated refers to 100°C or less, and the closer the temperature is to 100°C, the higher the sterilization effect can be. However, sterilization is usually sufficient even by heating from room temperature.

By the way, when the support is heated as in the method of the present invention,
As shown in FIG. 5, the maximum temperature is the lowest at the interior center 16, and increases in the order of the surface center 18 and the corner vicinity 17. On the other hand, when an object to be heated is normally irradiated with microwaves, a large amount of heat is removed from the surface of the object in contact with a low-temperature support, particularly from the edges. Therefore, surrounding the heated support with a preheated support is very effective in preventing heat radiation from the heated object. Further, when cooling, the vicinity of the corner 17 is most easily cooled, and the inner center 16 is least likely to be cooled.

<Function> In the method of the present invention, a support is warmed and heated to a temperature higher than the sterilization temperature, a package filled with an object to be heated such as a food is housed in the support, and heat sterilization is performed by irradiating the support with microwaves. ,
It is possible to prevent heat radiation from the surface of the heated object,
Stable sterilization performance can be obtained.

<Example I> A silicon-impregnated glass cloth laminate was used as the support, and a support made of glass filler-filled epoxy resin was used as the holder. This support was warmed and heated to a temperature of 140°C at the corner, and F, which is a sterilization index, was measured at each measurement point. 4a was measured. Further, as a package to be stored in the space of the support, a tray made of a three-layer sheet of polypropylene/ethylene vinyl alcohol copolymer/polypropylene and filled with 140 g of water was used. The tray was housed in a support with an optical fiber temperature needle attached to the center surface, at the time of sealing, and at the center of the interior, and microwave heating was performed until the inner center temperature of the tray reached 128°C. Further, as a comparative example, similar microwave heating was performed on a support whose support was not preheated. The results of this experiment are shown in Table 1.

Table 1 (Temperature unit 'C) As is clear from Table 1, in the method of the present invention, the F0 value at the surface of the package, especially at the corners and seals, increases compared to the conventional method, and the F0 value at the center surface and the center of the interior increases. approached. Furthermore, as shown in Table 2, the results of the sterilization test using cream stew showed that a stable sterilization effect was obtained.

Table 2 <Example 2> A silicon-impregnated glass cloth laminate was used as the support, and a support made of glass filler-filled epoxy resin was used as the holder. This support was warmed and heated to a temperature of 140° C. at the corner, and the F0 value, which is a sterilization index, was measured at each measurement point. Further, as a package to be stored in the space of the support, a tray made of a three-layer sheet of polypropylene/ethylene vinyl alcohol copolymer/polypropylene was used, which was filled with 140 g of water and heated to 70°C in advance. An optical fiber thermometer was attached to the center surface, at the time of sealing, and at the center of the interior, and the tray was housed in a support, and microwave heating was performed until the internal center temperature of the tray reached 128°C. Further, as a comparative example, similar microwave heating was performed on a support whose support was not preheated. The results of this experiment are shown in Table 3.

Table 3 Compared with the conventional method, the F0 value on the surface of the package, especially at the corners and at the sealing edge, increased and approached the F0 value at the center surface and the center of the interior. In addition, as shown in Table 4, the results of the sterilization test using cream stew showed that a stable sterilization effect was obtained.

Table 4 <Effects> By sterilizing food using the method of the present invention, stable sterilization can be achieved by suppressing heating variations, and microwave heating sterilization can be performed while maintaining the temperature of the actual food at the time of pre-cooking. This helped improve quality by saving energy and shortening sterilization time.

[Brief explanation of drawings]

Fig. 1 is a perspective view of the support used in the present invention, Fig. 2 is a perspective view of a package housed in this support, Fig. 3 is a sectional view of the support with the package housed therein, and Fig. 4 The figure is an explanatory diagram of a microwave heating sterilizer, and FIG. 5 is an explanatory diagram showing measurement points of heating temperature in an example. DESCRIPTION OF SYMBOLS 1... Support body, 4... Storage part 11... Bottom wall 14... Lid material 17... Corner part 2... Packaging body, 3... Holding part 5... Bag 6 ...Tray 12...Top wall 13...Container body 16...Inner center

Claims (1)

[Claims] (1) In a microwave heating sterilization method in which a package filled with the object to be heated is housed in a support made of a material that can transmit microwaves and has a storage section in the center, and sterilization is performed by irradiating and heating the package with microwaves. , a microwave heating sterilization method characterized by heating the support to a sterilization temperature or higher temperature in advance.